VIDO-InterVac, University of Saskatchewan, Saskatoon, Saskatchewan, Canada.
Parasitology and Animal Diseases Department, National Research Center, Dokki, Giza, Egypt.
J Virol. 2018 Sep 26;92(20). doi: 10.1128/JVI.00680-18. Print 2018 Oct 15.
The adenovirus E3 region encodes proteins that are not essential for viral replication The porcine adenovirus type 3 (PAdV-3) E3 region encodes three proteins, including 13.7K. Here, we report that 13.7K is expressed as an early protein, which localizes to the nucleus of infected cells. The 13.7K protein is a structural protein, as it is incorporated in CsCl-purified virions. The 13.7K protein appears to be essential for PAdV-3 replication, as mutant PAV13.7 expressing a mutated 13.7K could be isolated only in VIDO AS2 cells expressing the 13.7K protein. Analysis of PAV13.7 suggested that even in the presence of reduced levels of some late viral proteins, there appeared to be no effect on virus assembly and production of mature virions. Further analysis of CsCl-purified PAV13.7 by transmission electron microscopy revealed the presence of disrupted/broken capsids, suggesting that inactivation of 13.7K protein expression may produce fragile capsids. Our results suggest that the PAdV-3 E3 region-encoded 13.7K protein is a capsid protein, which appears to be essential for the formation of stable capsids and production of infectious progeny virions. Although E3 region-encoded proteins are involved in the modulation of leukocyte functions (N. Arnberg, Proc Natl Acad Sci U S A 110:19976-19977, 2013) and inducing a lytic infection of lymphocytes (V. K. Murali, D. A. Ornelles, L. R. Gooding, H. T. Wilms, W. Huang, A. E. Tollefson, W. S. Wold, and C. Garnett-Benson, J Virol 88:903-912, 2014), none of the E3 proteins appear to be a component of virion capsid or required for replication of adenovirus. Here, we demonstrate that the 13.7K protein encoded by the E3 region of porcine adenovirus type 3 is a component of progeny virion capsids and appears to be essential for maintaining the integrity of virion capsid and production of infectious progeny virions. To our knowledge, this is the first report to suggest that an adenovirus E3-encoded protein is an essential structural protein.
腺病毒 E3 区编码的蛋白对于病毒复制不是必需的。猪腺病毒 3 型（PAdV-3）的 E3 区编码三个蛋白，包括 13.7K。在这里，我们报告 13.7K 作为早期蛋白表达，定位于感染细胞的核内。13.7K 蛋白是一种结构蛋白，因为它存在于 CsCl 纯化的病毒粒子中。13.7K 蛋白似乎对 PAdV-3 的复制是必需的，因为表达突变 13.7K 的突变体 PAV13.7 只能在表达 13.7K 蛋白的 VIDO AS2 细胞中分离出来。对 PAV13.7 的分析表明，即使在一些晚期病毒蛋白水平降低的情况下，对病毒组装和成熟病毒粒子的产生似乎没有影响。用透射电子显微镜对 CsCl 纯化的 PAV13.7 进行进一步分析显示存在断裂/破裂的衣壳，表明 13.7K 蛋白表达失活可能产生脆弱的衣壳。我们的结果表明，PAdV-3 E3 区编码的 13.7K 蛋白是一种衣壳蛋白，似乎对稳定衣壳的形成和有感染性的子代病毒粒子的产生是必需的。尽管 E3 区编码的蛋白参与白细胞功能的调节（N.Arnberg，Proc Natl Acad Sci U S A 110：19976-19977，2013）和诱导淋巴细胞的裂解感染（V.K.Murali，D.A.Ornelles，L.R.Gooding，H.T.Wilms，W.Huang，A.E.Tollefson，W.S.Wold，和 C.Garnett-Benson，J Virol 88：903-912，2014），但 E3 蛋白似乎都不是病毒粒子衣壳的组成部分，也不是腺病毒复制所必需的。在这里，我们证明了猪腺病毒 3 型 E3 区编码的 13.7K 蛋白是子代病毒粒子衣壳的组成部分，并且似乎对维持病毒粒子衣壳的完整性和产生有感染性的子代病毒粒子是必需的。据我们所知，这是第一个表明腺病毒 E3 编码蛋白是必需的结构蛋白的报告。
